Lubricating oil additive



Patented Mar. 10, 1953 LUBRICATING OIL ADDITIV E John P. Mcllermott, Roselle, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application April 12, 1950, Serial No. 155,553

Claims. 1

This invention relates to lubricants and other organic materials subject to deterioration in the presence of oxygen and to an additive which serves to inhibit such oxidation.

In accordance with the present invention a new class of organic compositions are described which are particularly useful as additives for mineral lubricating oils used in internal combustion engines, in which they act as inhibitors of oxidation. Thus, the additives serve as an aid in the prevention of ring sticking, piston skirt varnish formation, deposition of sludge, and the like. They are particularly useful in inhibiting the normal corrosiveness of the oil when in contact with copper-lead, cadmium-silver and other similar bearings now widely used in automotive engines. These compounds are likewise suitable for use as antioxidants in other hydrocarbon materials and in organic materials generally'where the material is susceptible to deterioration in the presence of oxygen.

The new class of antioxidant compounds are disulflde derivatives of organo-substituted thiophosphoric acids, wherein the organic groups of the thiophosphoric acids are ester groups derived from esters of hydroxy-carboxylic acids. These compounds may be more precisely defined by the formula Roocmvo s where R is an alkyl radical, straight chain or branched, containing 4 to 18 carbon atoms, R is a saturated aliphatic hydrocarbon radical, straight chain or branched, containing 1 to 18 carbon atoms, and n is an integer from 1 to 3.

The new additives may be readily prepared by first reacting an ester of a hydroxy-carboxylic acid with phosphorus pentasulfide to form an organo-substituted thiophosphoric acid, then further reacting this acid product with an oxidizing agent such as iodine, potassium triiodide, ferric chloride, an oxide of nitrogen, or oxygen itself. It is not intended, however, that the invention be limited in any manner by the oxidizing agent used. The formation of the organo-substituted 2 dithiophosphoric acid disulfide is represented by the following equations:

Suitable hydroxy-acids which may be employed in the preparation of esters which are reacted with phosphorus pentasulfide to form the organo-substituted dithiophosphoric acids include the following: glycollic acid, lactic acid, hydracrylic acid, the hydroxybutyric acids, 12- hydroxystearic acid, tartronic acid, malic acid, and citric acid. These acids may be esterified with alcohols such as the following: n-butyl alcohol, tert.-butyl alcohol, 2-ethylhexyl alcohol, tert.-octyl alcohol, n-dodecyl alcohol, lauryl aloohol, tert.-dodecyl alcohol, and a commercial mixture of C10 to C18 primary alcohols derived from coconut oil and known as Lorol B" alcohol. A group of alcohols especially adapted for use in connection with the present invention are the so-called 0x0 alcohols, prepared by the reaction of carbon monoxide and hydrogen upon the olefins obtainable from petroleum products and hydrogenation of the resulting aldehydes. Materials such as diisobutylene and C1 olefins are suitable for this purpose, as well as higher molecular weight olefinic materials. The alcohols obtained in this manner are primary alcohols and normally have a branched chain structure.

The additives of the present invention are preferably added to lubricating oils in proportions of about 0.01 to 2.0% by weight, and in some cases it may be necessary to employ quantities which are above or below this range. The proportions giving the best results will vary somewhat according to the nature of the additive and of the base stock to which it is added. For commercial purposes, it is convenient to prepare concentrated oil solutions in which the.

amount of additive in the composition ranges from 25% to 50% by weight, and to transport and store them in such form. In preparing a lubricating oil composition for use as a crankcase lubricant, the additive concentrate is merely blended with the base oil in the required amount.

Below are given detailed descriptions of the preparation of examples of the lubricating oil additives described above as well as laboratory tests and engine tests in which the oil containing the additive was used as the lubricant. It is to be understood that these examples are given as illustrations of the present invention and are not to be construed as limiting the scope thereof in any way.

Example I A B-necked, l-liter flask equipped with a stirrer, thermometer, and reflux condenser was charged with 146 g. (1 mol) of butyl lactate and 55.5 g. (0.25 mol) of P285. This mixture was heated at 120 C. for one hour with rapid stirring followed by filtration to remove asmall amount of unreacted P285. The filtrate was transferred to a 3-necked, 2-liter flask, after which a solution of 41.4 g. (0.6 mol) of NaNOz in 100 cc. water was added over a period of 45 minutes with vigorous stirring. Following this, 60 g. (0.3 mol) of 50% aqueous H2804 was added dropwise over a period of one hour. During the latter two steps the temperature was maintained at 25-30 C. by means of an ice bath. After stirring for an additional hour at room temperature, 200 cc. of CHCh was added to dissolve the reaction product. The CHCla layer was separated and washed with NaHCOx solution until the wash water was alkaline, and further washed with distilled water. The organic layer was dried over KzCOa, after which the solvent was evaporated on a steam bath. A clear reddish liquid was obtained, which upon analysis was found to contain 8% phosphorus and 16.9% sulfur.

Example 2 Lorol citrate was prepared by esterifying Lorol B alcohol with citric acid. A 3-necked, 1-liter flask equipped with stirrer and thermometer was charged with 189.5 g. (0.25 mol) of Lorol citrate and 14 g. (0.063 mol) of P285. The reaction mixture was heated at 125 C. for one hour and filtered to remove a small amount of unreacted PzSs. During this step about 50 cc. of CHCh was added to the viscous product to hasten the filtration. The reaction was then completed as described in Example 1, using 10.4 g. (0.15 mol) of NaNOz in 50 cc. water and 15 g. (0.08 mol) of 50% aqueous H2804. A dark viscous liquid was obtained which upon analysis was found to contain 1.2% phosphorus and 2.2% sulfur.

Emmple 3.Laboratory bearing corrosion test Blends were prepared containing 0.25% by weight of each of the additives prepared as described in Examples 1 and 2, using as a base oil an extracted Mid-Continent paraffinic lubricating oil of SAE grade. Samples of these blends and a sample of the unblended base oil were submitted to a laboratory test designed to measiu'e the efiectiveness of the additive in inhibiting the corrosiveness of a typical mineral lubricating oil toward the surfaces of copper-lead bearings. The tests were conducted as follows:

500 cc. of the oil was placed in a glass oxidation tube (13 inches long and 2% inches in diameter) fitted at the bottom with a A inch air inlet tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating bath so that the oil temperature was maintained at 325 F. during the test. Two quarter sections of automotive bearings of copper-lead alloy of known weight having a total area of 25 sq. cm. were attached to opposite sides of a stainless steel rod which was then immersed in the test oil and rotated at 600 R. P. M., thus providing sufiicient agitation of the sample during the test. Air was then blown through the oil at the rate or 2 cu. .ft. per hour. At the end of each four-hour period the hearings were removed, washed with naphtha and weighed to determine the amount of loss by corrosion. The bearings were then repolished (to increase the severity of the test), reweighed, and then subjected to the test for additional four-hour periods in like manher. The results are given in the following table as corrosion life, which indicates the number of hours required for the bearings to lose mg. in weight, determined by interpolation of the data obtained in the various periods.

Example 4.-Lauson engine test The product prepared as described in Example 1 was tested in a Lauson engine, using blends of 1% by weight of the additive in a solvent extracted coastal oil of SAE 30 grade. For comparison, a sample of the unblended base oil was likewise tested. Each test was conducted for a period of 20 hours, the Lauson engine being operated at 1800 R. P. M. with a 1.5 indicated kilowatt load, 295 F. oil temperature and 300 F. water jacket temperature. Observations were made on the loss in weight of the copper-lead bearing during each test. The results are shown in the following table:

The products of the present invention may be employed not only in ordinary hydrocarbon lubricating oils but also in the heavy duty type of lubricating oils which have been compounded with such detergent type additives as metal soaps, metal petroleum sulfonates, metal phenates, metal alcoholates, metal alkyl phenol sulfides, metal organo phosphates, phosphites, thiophospha-tes, and thiophosphites, metal xanthates and thioxanthates, metal thiocarbamates, and the like. Other types of additives, such as phenols and phenol sulfides, may also be present.

The lubricating oil base stock used in the compositions of this invention may be straight mineral lubricating oils or distillates derived from paraffinic, naphthenic, asphaltic or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constituents have been carefully removed. The oils may be refined by conventional methods using acid, alkali and/or clay or other agents such as aluminum chloride, or they may be extracted oils produced by solvent extraction with solvents such as phenol, sulfur dioxide, etc. Hydrogenated oils or white oils may be employed as well as synthetic oils prepared, for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products. In certain instances cracking oil tar fractions and coal tar or shale oil distillates may also be used. Also, for special applications, animal, vegetable or fish oils or their hydrogenated or voltolized products may be employed in admixtures with mineral oils.

For the best results the base stock chosen should normally be an oil which with the new additive present gives the optimum performance in the service contemplated. However, since one advantage of the additives is that their us also makes feasible the employment of less satisfactory mineral oils, no strict rule can be laid down for the choice of the base stock. The additives are normally sufiiciently soluble in the base stock, but in some cases auxiliary solvent agents may be used. The lubricating oils will usually range from about 40 to 150 seconds (Saybolt) viscosity at 210 F. The viscosity index may range from 0 to 100 or even higher.

Other agents than those which have been mentioned may be present in the oil composition, such as dyes, pour point depressants, heat thickened fatty oils, sulfurized fatty oils, sludge dispersers, anti-oxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, and the like.

Assisting agents which are particularly desirable as plasticizers and defoamers are the higher alcohols having preferably 8-20 carbon atoms, e. g., octyl alcohol, lauryl alcohol, stearyl alcohol, and the like.

In addition to being employed in lubricants, the additives of the present invention may also be used in other mineral oil products such as motor fuels, hydraulic fluids, torque converter fluids, cutting oils, flushing oils, turbine oils, transformer oils, industrial oils, process oils, and the like, and generally as antioxidants in mineral oil products. They may also be used in gear lubricants, greases and other products containing mineral oils as ingredients.

What is claimed is:

1. A composition consisting essentially of a mineral lubricating oil and 0.01 to 2% by weight of a compound of the formulawhere R is an alkyl radical containing 4 to 18 carbon atoms, R is a saturated aliphatic hydromineral lubricating oil and 0.1 to 2 by weight of a compound of the formula- CllHz (3H3 ROOCCHO s s OCHCOOR noooono s-s o CHCOOR CH3 H3 where R is an alkyl radical containing 4 to 18 carbon atoms.

5. A composition according to claim 4 in which R of the formula represents C4H9.

6. A composition consisting essentially of a mineral lubricating oil and 0.1 to 2% by weight of a compound of the formula- COOR l (ROOCCHMCO S S (ROOCCHmOO s oowmooorm 00R COOR where R is an alkyl radical containing 4 to 18 carbon atoms.

'7. A composition according to claim 6 in which R of the formula represents a straight chain alkyl radical, the additive consisting of a mixture of such compounds in which the number of carbon atoms in the radical R is from 10 to 18.

8. A composition consisting essentially of a mineral lubricating oil and an additive as defined in claim 1, the amount of said additive in the composition being 25 to 50% by weight.

9. A composition consisting essentially of a mineral lubricating oil and an additive as defined in claim 5, the amount of said additive in the composition being 25 to 50% by weight.

10. A composition consisting essentially of a mineral lubricating oil and an additive as defined in claim '7, the amount of said additive in the composition being 25 to 50% by weight.

JOHN P. MCDERMOTT.

REFERENCES CITED UNITED STATES PATENTS Name Date Mikeska June 15, 1948 Number 

1. A COMPOSITION CONSISTING ESSENTIALLY OF A MINERAL LUBRICATING OIL AND 0.01 TO 2% BY WEIGHT OF A COMPOUND OF THE FORMULA- 